Composite piston ring seal for axially and   circumferentially translating ducts

ABSTRACT

A seal system is provided. The seal system may comprise a first duct having an annular geometry, a second duct overlapping the first duct in a radial direction, and a seal disposed between the first duct and the second duct. The seal may comprise a groove defined by the first duct and a piston configured to slideably engage the groove.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional of, and claims priority to, U.S.application Ser. No. 14/727,475, filed Jun. 1, 2015 and titled“COMPOSITE PISTON RING SEAL FOR AXIALLY AND CIRCUMFERENTIALLYTRANSLATING DUCTS.” The '475 application is hereby incorporated byreference in its entirety.

GOVERNMENT LICENSE RIGHTS

This disclosure was made with Government support under Contract No.FA8650-09-D-2923 awarded by the United States Air Force. The U.S.Government has certain rights in the disclosure.

FIELD

The present disclosure relates to gas turbine engines, and, morespecifically, to gas path duct sealing for gas turbine engines.

BACKGROUND

Gas turbine engines may have various gas-flow streams that may be keptseparate from one another. The gas-flow streams may be separated bycomponents including cowls and seals. A pair of annular cowls may alignwith one another, but relative translation in axial and circumferentialdirections may create varying relative motion between the cowls duringoperation. The varying relative motion may be sealed to maintainseparate gas-flow streams, but the varying relative may tear seals orrender the seals ineffective. For example, finger seals in such aconfiguration may risk catching an edge of the nozzle since a cowl maymove diagonally across the fingers.

SUMMARY

A gas turbine engine may comprise a compressor, a combustor disposed aftof the compressor and in fluid communication with the compressor, and aturbine aft of the combustor and in fluid communication with thecombustor. An inner duct may be disposed radially outward from theturbine, and an outer duct may be disposed radially outward from theinner duct. A groove may be formed in the inner duct, and a piston maybe configured to slideably engage the groove.

In various embodiments, the piston may comprise a fibrous material. Thepiston may also comprise at least one of a glass fiber-reinforcedpolymer (GFRP) or an aramid fiber-reinforced polymer (AFRP). A bumpermay be bonded to the inner duct. The bumper may comprise at least one ofa GFRP or an AFRP. The bumper may comprise an annular geometry. Thebumper may be disposed in a recess in the inner duct. The piston maycomprise an elliptical shape. A spring may be disposed in the groove.The piston may be configured to bottom in the groove and locate theinner duct separate from the outer duct.

A seal system may comprise a first duct having an annular geometry, asecond duct overlapping the first duct in a radial direction, and a sealdisposed between the first duct and the second duct. The seal maycomprise a groove defined by the first duct and a piston configured toslideably engage the groove.

In various embodiments, the piston may include a fibrous material. Thepiston may comprise a GFRP or an AFRP. A bumper may be bonded to thefirst duct. The bumper may comprise at least one of a GFRP or an AFRP,and may also have an annular geometry. The bumper may be disposed in arecess in the first duct. The piston may comprise an elliptical shape. Aspring may be disposed in the groove.

A seal may comprise a groove defined by a first duct. The groove mayhave metallic walls. A piston may include a composite material andconfigured to slideably engage the groove.

The foregoing features and elements may be combined in variouscombinations without exclusivity, unless expressly indicated otherwise.These features and elements as well as the operation thereof will becomemore apparent in light of the following description and the accompanyingdrawings. It should be understood, however, the following descriptionand drawings are intended to be exemplary in nature and non-limiting.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject matter of the present disclosure is particularly pointed outand distinctly claimed in the concluding portion of the specification. Amore complete understanding of the present disclosure, however, may bestbe obtained by referring to the detailed description and claims whenconsidered in connection with the figures, wherein like numerals denotelike elements.

FIG. 1 illustrates an exemplary gas-turbine engine, in accordance withvarious embodiments;

FIG. 2 illustrates a split ring seal axially adjacent to a cowl that isprone to axial and circumferential translation, in accordance withvarious embodiments;

FIG. 3 illustrates a cross section of a split ring seal coupled to anouter duct and comprising a wave spring, in accordance with variousembodiments;

FIG. 4 illustrates a cross section of a split ring seal coupled to anouter duct and comprising composite bumper pads between the outer ductand inner duct, in accordance with various embodiments;

FIG. 5 illustrates a cross section of a split ring seal coupled to anouter duct and comprising a composite bumper ring between the inner ductand outer duct, in accordance with various embodiments;

FIG. 6 illustrates a cross section of a split ring seal coupled to aninner duct and comprising a wave spring, in accordance with variousembodiments;

FIG. 7 illustrates a cross section of a split ring seal coupled to aninner duct and comprising composite bumper pads between the outer ductand inner duct, in accordance with various embodiments; and

FIG. 8 illustrates a cross section of a split ring seal coupled to aninner duct and comprising a composite bumper ring between the inner ductand outer duct, in accordance with various embodiments.

DETAILED DESCRIPTION

The detailed description of exemplary embodiments herein makes referenceto the accompanying drawings, which show exemplary embodiments by way ofillustration. While these exemplary embodiments are described insufficient detail to enable those skilled in the art to practice theexemplary embodiments of the disclosure, it should be understood thatother embodiments may be realized and that logical changes andadaptations in design and construction may be made in accordance withthis disclosure and the teachings herein. Thus, the detailed descriptionherein is presented for purposes of illustration only and notlimitation. The steps recited in any of the method or processdescriptions may be executed in any order and are not necessarilylimited to the order presented.

Furthermore, any reference to singular includes plural embodiments, andany reference to more than one component or step may include a singularembodiment or step. Also, any reference to attached, fixed, connected orthe like may include permanent, removable, temporary, partial, fulland/or any other possible attachment option. Additionally, any referenceto without contact (or similar phrases) may also include reduced contactor minimal contact. Surface shading lines may be used throughout thefigures to denote different parts but not necessarily to denote the sameor different materials.

As used herein, “aft” refers to the direction associated with the tail(e.g., the back end) of an aircraft, or generally, to the direction ofexhaust of the gas turbine. As used herein, “forward” refers to thedirection associated with the nose (e.g., the front end) of an aircraft,or generally, to the direction of flight or motion.

As used herein, “distal” refers to the direction radially outward, orgenerally, away from the axis of rotation of a turbine engine. As usedherein, “proximal” refers to a direction radially inward, or generally,towards the axis of rotation of a turbine engine.

With reference to FIG. 1, an exemplary gas turbine engine 100 is shown,in accordance with various embodiments. Gas turbine engine 100 maycomprise a fan 102 with a nose cone 104 disposed forward of fan 102.Nose cone 104 may rotate with fan 102 as fan 102 drives airflow intocompressor 106 and bypass ducts 110. Compressor 106 may be in fluidcommunication with combustor 112 with the airflow exiting compressor 106and entering combustor 112. A fuel-air mixture may be ignited incombustor 112.

In various embodiments, combustor 112 may be in fluid communication withturbine 108 disposed aft of combustor 112. Combusted gas from combustor112 expands across turbine 108 to provide rotational energy tocompressor 106 and fan 102. Rotating components of gas turbine engine100 such as the turbine 108 and compressor 106 may be configured torotate about axis A.

In various embodiments, tail cone 114 may be disposed aft of turbine108. An augmentor liner may also be disposed aft of turbine 108. Anozzle comprising a divergent nozzle section 122 and a convergent nozzlesection 126 may be disposed aft of augmentor liner 116. A proximalbypass duct 120 may be disposed radially outward from compressor 106,combustor 112, and turbine 108. A distal bypass duct 124 may be disposedradially outward from proximal bypass duct 120. The ducting of proximalbypass duct 120 and distal bypass duct 124 may include sealing section118.

Large ducting that undergoes movement, such as proximal bypass duct 120and distal bypass duct 124, may implement sealing between ducts tomaintain ducting during periods of movement. Sealing section 118 maycomprise a split ring seal, as described in detail below, to maintainsealing while in duct sections when movement would otherwise cause fluidleaks.

With reference to FIG. 2, sealing section 118 is shown, in accordancewith various embodiments. Sealing section 118 may comprise outer duct146 and forward cowling 148. Outer duct 146 and forward cowling 148 mayboth comprise a cylindrical or annular geometry. During operation,forward cowling 148 and outer duct 146 may translate relative to oneanother in an axial direction (i.e., forward and aft directions) as wellas a circumferential direction (i.e., a rotational direction). Innerduct 140 may be disposed forward of outer duct 146. Linkage system 142may comprise swiveling, rigid arms that cause the outer duct 146 to movecircumferentially relative to inner duct 140 in response to outer duct146 moving axially relative to inner duct 140.

With reference to FIG. 3, a seal system 150 is shown, in accordance withvarious embodiments. Seal system 150 may be a split ring seal (alsoreferred to herein as a piston seal) disposed between a forward portionof outer duct 146 and an aft portion of inner duct 140 at a locationwhere outer duct 146 and inner duct 140 overlap in a radial direction.Seal system 150 may comprise groove 168 formed in, and defined by, innerduct 140. A piston 164 may contact and separate from outer duct 146 andslideably engage groove 168 of inner duct 140. Inner duct 140 and outerduct 146 may each be made from metallic materials such as titanium,aluminum, stainless steel, alloyed metals, or other suitable metallicmaterials. The groove 168 defined by inner duct 140 may thus havemetallic sidewalls.

In various embodiments, piston 164 may comprise a composite materialhaving favorable wear characteristics when sliding against metals. Forexample, piston 164 may comprise glass fiber-reinforced polymer (GFRP)or an aramid fiber-reinforced polymer (AFRP). The resin used in piston164 may be selected for performance at high temperatures. For example,the resin used in piston 164 may be selected to operate at temperaturesof about 600° F. (315° C.), wherein the term about in this context means+/−50° F. Piston 164 may comprise an annular or ring-shaped flangeprotruding from outer duct 146 having a circular geometry. The annularshape of piston 164 may also be elongated in some locations so that thecross sectional shape of piston 164 is elliptical or otherwise variesfrom a circular geometry. The positions of groove 168 and piston 164 maybe reversed with groove 168 disposed on outer duct 146 and piston 164disposed on inner duct 140. The fibers in piston 164 may be oriented toprovide a desired stiffness in various directions (e.g., axially,circumferentially, and radially) at various locations of piston 164 sothat piston 164 may deflect and deform in a desired, predeterminedshape.

In various embodiments, a spring 162 may be disposed between groove 168and piston 164 to provide mechanical resistance to piston 164 enteringgroove 168. Spring 162 may become fully compressed in a radial directionin response to piston 164 traveling a predetermined distance into groove168 with spring 162 becoming a load bearing member. Spring 162 may beomitted provided that piston 164 has sufficient dimensions to “bottomout” in groove 168 (i.e., translate to a bottom surface of the groove)before outer duct 146 contacts inner duct 140 and thereby locate outerduct 146 separate from inner duct 140. Thus, seal system 150 may preventor limit metal-to-metal contact between outer duct 146 and inner duct140. Piston 164 may be made of composite materials and may be lighter inweight than a metal piston. Piston 164 may have a ring configuration mayhave a diameter of approximately 50 inches (127 cm).

With reference to FIG. 4, seal system 150 comprising bumper 202 betweenthe outer duct 146 and inner duct 190 is shown, in accordance withvarious embodiments. Seal system 150 of FIG. 4 is similar to seal system150 of FIG. 3. In FIG. 4, seal system 150 comprises groove 198 formed ininner duct 190. Piston 194 may slideably engage groove 198 with a spring192 disposed at a proximal end of piston 194. Piston 194 may havedimensions to maintain gap 200 between outer duct 146 and inner duct 190in response to outer duct 146 contacting bumper 202. Bumper 202 may bemade from a composite material similar to piston 194 such as a GFRP,AFRP, or other fibrous material within a resin matrix. Bumper 202 maythus exhibit advantageous wear characteristics in response to slidingand/or contacting outer duct 146.

In various embodiments, bumper 202 may be bonded to inner duct 190 tolimit deflection and prevent piston 194 from bottoming out in groove 198(i.e., contacting the radial surface of the groove by traveling radiallyinto the groove). Bumper 202 may be a plurality of discrete bumpersbonded about an outer diameter of inner duct 190. Bumper 202 may extendforward of outer duct 146 in an axial direction so that bumper 202 ispartially exposed from outer duct 146 when viewed in a radially inwarddirection. Bumper 202 may also be a continuous annular bumper disposedabout an outer diameter of inner duct 190.

With reference to FIG. 5, seal system 150 comprising bumper 222 recessedin a groove between the outer duct 146 and inner duct 210 is shown tomaintain a spacing 220, in accordance with various embodiments. Sealsystem 150 of FIG. 5 is similar to seal system 150 of FIG. 4. In FIG. 5,seal system 150 comprises piston 214 slideably coupled to groove 218.Groove 218 may be defined by inner duct 190. Piston 214 may slideablyengage outer duct 146. Bumper 222 may comprise a bumper ring or annuluslodged in and/or bonded to a recess in inner duct 210 in axial serieswith piston 214 and groove 218. Spring 212 may optionally be included tolocate piston 214 radially relative to groove 218. Outer duct 146 maycontact bumper 222 to limit the deflection of piston 214 into groove218. Bumper 222 may be made from a composite material similar to piston214 such as GFRP, AFRP, or other fibrous material within a resin matrix.Bumper 222 may thus exhibit advantageous wear characteristics inresponse to sliding and/or contacting outer duct 146.

With reference to FIG. 6, a seal system 230 is shown, in accordance withvarious embodiments. Seal system 230 may include a piston seal disposedbetween a forward portion of outer duct 232 and an aft portion of innerduct 234 at a location where outer duct 232 and inner duct 234 overlapin a radial direction. Inner duct 234 and outer duct 232 may each bemade from metallic materials such as titanium, aluminum, stainlesssteel, alloyed metals, or other suitable metallic materials. The groove168 defined by inner duct 234 may thus have metallic sidewalls. Sealsystem 230 may comprise groove 236 formed in, and defined by, outer duct232. A piston 238 may contact and separate from inner duct 234 andslideably engage groove 236 of outer duct 232. Outer duct 232 and innerduct 234 may each be made from metallic materials such as titanium,aluminum, stainless steel, alloyed metals, or other suitable metallicmaterials. The groove 236 defined by outer duct 232 may thus havemetallic sidewalls.

In various embodiments, piston 238 may comprise a composite materialhaving favorable wear characteristics when sliding against metals. Forexample, piston 238 may comprise GFRP or an AFRP. The resin used inpiston 238 may be selected for performance at high temperatures. Forexample, the resin used in piston 238 may be selected to operate attemperatures of about 600° F. (315° C.), wherein the term about in thiscontext means +/−50° F. Piston 238 may comprise an annular orring-shaped flange protruding from inner duct 234 having a circulargeometry. The annular shape of piston 238 may also be elongated in somelocations so that the cross sectional shape of piston 238 is ellipticalor otherwise varies from a circular geometry. The positions of groove236 and piston 238 may be reversed with groove 236 disposed on innerduct 234 and piston 238 disposed on outer duct 232 (as shown in FIG. 3).The fibers in piston 238 may be oriented to provide a desired stiffnessin various directions (e.g., axially, circumferentially, and radially)at various locations of piston 238 so that piston 238 may deflect anddeform in a desired, predetermined shape.

In various embodiments, a spring 240 may be disposed between groove 236and piston 238 to provide mechanical resistance to piston 238 enteringgroove 236. Spring 240 may become fully compressed in a radial directionin response to piston 238 traveling a predetermined distance into groove236 with spring 240 becoming a load bearing member. Spring 240 may beomitted provided that piston 238 has sufficient dimensions to “bottomout” in groove 236 (i.e., translate to a bottom surface of the groove)before inner duct 234 contacts outer duct 232 and thereby locate innerduct 234 separate from outer duct 232. Thus, seal system 230 may preventor limit metal-to-metal contact between inner duct 234 and outer duct232. Piston 238 may be made of composite materials and may be lighter inweight than a metal piston. Piston 238 may have a ring configuration mayhave a diameter of approximately 50 inches (127 cm).

With reference to FIG. 7, seal system 250 comprising bumper 260 betweenthe inner duct 254 and outer duct 252 is shown, in accordance withvarious embodiments. Seal system 250 of FIG. 7 is similar to seal system230 of FIG. 6. In FIG. 7, seal system 250 comprises groove 256 formed inouter duct 252. Piston 258 may slideably engage groove 256. Piston 258may have dimensions to maintain gap 200 between inner duct 254 and outerduct 252 in response to inner duct 254 contacting bumper 260. Bumper 260may be made from a composite material similar to piston 258 such as aGFRP, AFRP, or other fibrous material within a resin matrix. Bumper 260may thus exhibit advantageous wear characteristics in response tosliding and/or contacting inner duct 254.

In various embodiments, bumper 260 may be bonded to outer duct 252 tolimit deflection and prevent piston 258 from bottoming out in groove 256(i.e., contacting the radial surface of the groove by traveling radiallyinto the groove). Bumper 260 may be a plurality of discrete bumpersbonded about an outer diameter of outer duct 252. Bumper 260 may extendforward of groove 256 in an axial direction so that bumper 260 ispartially exposed from inner duct 254 when viewed in a radially outwarddirection. Bumper 260 may also be a continuous annular bumper disposedabout an inner diameter of outer duct 252.

With reference to FIG. 8, seal system 270 comprising bumper 280 recessedin a groove between the outer duct 272 and inner duct 274 is shown, inaccordance with various embodiments. Seal system 270 is similar to sealsystem 250 of FIG. 7. In FIG. 8, seal system 270 comprises piston 276slideably coupled to groove 278. Groove 278 may be defined by outer duct272. Piston 276 may slideably engage with inner duct 274. Bumper 280 maycomprise a bumper ring or annulus lodged in and/or bonded to a recess ininner duct 274 in axial series with piston 276 and groove 278. A springmay be included to locate piston 276 radially relative to groove 278.Inner duct 274 may contact bumper 222 to limit the deflection of piston276 into groove 278. Bumper 222 may be made from a composite materialsimilar to piston 276 such as GFRP, AFRP, or other fibrous materialwithin a resin matrix. Bumper 222 may thus exhibit advantageous wearcharacteristics in response to sliding and/or contacting inner duct 274.

In various embodiments, the seal systems 150 illustrated in FIGS. 3-8may be formed by rolling layers of fibrous material around an ellipticalor circular spindle, depending on the desired shape of piston 164. Anelliptical spindle shape provides even diametric tension when compressedinto a circular housing. A resin matrix may be deposited in and aboutthe fibrous material and cured to form piston 164. Fibrous material maybe oriented to produce high modulus and tensile strength weave with alow modulus orientation on the compression side to reduce compressivestresses.

Benefits and other advantages have been described herein with regard tospecific embodiments. Furthermore, the connecting lines shown in thevarious figures contained herein are intended to represent exemplaryfunctional relationships and/or physical couplings between the variouselements. It should be noted that many alternative or additionalfunctional relationships or physical connections may be present in apractical system. However, the benefits, advantages, and any elementsthat may cause any benefit or advantage to occur or become morepronounced are not to be construed as critical, required, or essentialfeatures or elements of the disclosure. The scope of the disclosure isaccordingly to be limited by nothing other than the appended claims, inwhich reference to an element in the singular is not intended to mean“one and only one” unless explicitly so stated, but rather “one ormore.” Moreover, where a phrase similar to “at least one of A, B, or C”is used in the claims, it is intended that the phrase be interpreted tomean that A alone may be present in an embodiment, B alone may bepresent in an embodiment, C alone may be present in an embodiment, orthat any combination of the elements A, B and C may be present in asingle embodiment; for example, A and B, A and C, B and C, or A and Band C.

Systems, methods and apparatus are provided herein. In the detaileddescription herein, references to “various embodiments”, “oneembodiment”, “an embodiment”. “an example embodiment”, etc., indicatethat the embodiment described may include a particular feature,structure, or characteristic, but every embodiment may not necessarilyinclude the particular feature, structure, or characteristic. Moreover,such phrases are not necessarily referring to the same embodiment.Further, when a particular feature, structure, or characteristic isdescribed in connection with an embodiment, it is submitted that it iswithin the knowledge of one skilled in the art to affect such feature,structure, or characteristic in connection with other embodimentswhether or not explicitly described. After reading the description, itwill be apparent to one skilled in the relevant art(s) how to implementthe disclosure in alternative embodiments.

Furthermore, no element, component, or method step in the presentdisclosure is intended to be dedicated to the public regardless ofwhether the element, component, or method step is explicitly recited inthe claims. No claim element herein is to be construed under theprovisions of 35 U.S.C. 112(f), unless the element is expressly recitedusing the phrase “means for.” As used herein, the terms “comprises”,“comprising”, or any other variation thereof, are intended to cover anon-exclusive inclusion, such that a process, method, article, orapparatus that comprises a list of elements does not include only thoseelements but may include other elements not expressly listed or inherentto such process, method, article, or apparatus.

What is claimed is:
 1. A seal system, comprising: a first duct having anannular geometry; a second duct overlapping the first duct in a radialdirection; a seal disposed between the first duct and the second duct,the seal comprising: a groove defined by the second duct; and a pistonconfigured to slideably engage the groove.
 2. The seal system of claim1, wherein the piston comprises a fibrous material.
 3. The seal systemof claim 2, wherein the piston comprises a glass fiber-reinforcedpolymer (GFRP) or an aramid fiber-reinforced polymer (AFRP).
 4. The sealsystem of claim 1, further comprising a bumper bonded to the secondduct.
 5. The seal system of claim 4, wherein the bumper comprises atleast one of a glass fiber-reinforced polymer (GFRP) or an aramidfiber-reinforced polymer (AFRP).
 6. The seal system of claim 5, whereinthe bumper comprises the annular geometry.
 7. The seal system of claim5, wherein the bumper is disposed in a recess in the second duct.
 8. Theseal system of claim 1, wherein the piston comprises an ellipticalshape.
 9. The seal system of claim 1, further comprising a springdisposed in the groove.
 10. A gas turbine engine, comprising: acompressor; a combustor disposed aft of the compressor and in fluidcommunication with the compressor; a turbine aft of the combustor and influid communication with the combustor; an inner duct radially outwardfrom the turbine; an outer duct radially outward from the inner duct; agroove formed in the outer duct; and a piston configured to slideablyengage the groove.
 11. The gas turbine engine of claim 10, wherein thepiston comprises a fibrous material.
 12. The gas turbine engine of claim11, wherein the piston comprises at least one of a glassfiber-reinforced polymer (GFRP) or an aramid fiber-reinforced polymer(AFRP).
 13. The gas turbine engine of claim 10, further comprising abumper bonded to at least one of the outer duct or the inner duct. 14.The gas turbine engine of claim 13, wherein the bumper comprises atleast one of a glass fiber-reinforced polymer (GFRP) or an aramidfiber-reinforced polymer (AFRP).
 15. The gas turbine engine of claim 14,wherein the bumper comprises an annular geometry.
 16. The gas turbineengine of claim 15, wherein the bumper is disposed in a recess in the atleast one of the outer duct or the inner duct.
 17. The gas turbineengine of claim 15, wherein the bumper is configured to prevent thepiston from contacting a radial surface of the groove.
 18. The gasturbine engine of claim 10, wherein the piston comprises an ellipticalshape.
 19. The gas turbine engine of claim 10, further comprising aspring disposed in the groove.
 20. The gas turbine engine of claim 11,wherein the piston is configured to contact a radial surface of thegroove prior to the inner duct contacting the outer duct.